Causes of slope failure in ground
Slope is the proportion of the vertical rise to the horizontal space ascertained on the ground for that vertical rise
Slope is measured as a percentage and the calculation process is similar to the gradient. Transfer the rise and run to the similar units and then divide the rise with the run. Multiply this number with 100 to get the percentage slope. As for example, 3" rise divided by 36" run = .083 x 100 = an 8.3% slope.
Also read : TYPES OF SHORING FOR EXCAVATION
Slope failure occurs due to the following factors :-
- Extreme Rainfall
- Change in the level of water
- Secretion in water flow
- Volcanic blast
- Earthquake shivering
- Human activity
- Erosion
The wind and running water leads to erosion of top surface of slope and transforms the slope steep and as a result the tangential element of driving force is raised.
Secretion in water flow
Secretion forces in the sloping direction adjoin to gravity forces and transform the slope yielding to instability.
The pore water pressure reduces the stability of shear. This condition is vital for the downstream slope.
Abrupt drawdown
In such a case, there is reversal in the direction flow and leads to saturated unit weight when the shearing resistance is reduced because of pore water pressure that fails to disperse instantly.
Rainfall
Rainfall for prolong periods soak, soften and decay soils.
Water penetrates into subsisting cracks and impair foundational soil layers and results in collapsing of slope. As for instance mud slides.
Earthquake
It causes dynamic shear forces.
Besides, pore water pressure is formed abruptly and the existing shear strength is decreased significantly.
External loading
Excessive loads which are provided on top of the slope raise the gravitational forces which result in collapsing of slope.
Construction activities (at the foot of the slope)
The slopes become steep due to excavation at the base of the sloping surface and as a result the gravitational forces are raised which result in collapsing of slope.
